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<head><meta charset="utf-8"><title>Why are there two tracking issues for SIMD? · general · Zulip Chat Archive</title></head>
<h2>Stream: <a href="https://rust-lang.github.io/zulip_archive/stream/122651-general/index.html">general</a></h2>
<h3>Topic: <a href="https://rust-lang.github.io/zulip_archive/stream/122651-general/topic/Why.20are.20there.20two.20tracking.20issues.20for.20SIMD.3F.html">Why are there two tracking issues for SIMD?</a></h3>

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<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/122651-general/topic/Why%20are%20there%20two%20tracking%20issues%20for%20SIMD%3F/near/233117075" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Joshua Nelson <a href="https://rust-lang.github.io/zulip_archive/stream/122651-general/topic/Why.20are.20there.20two.20tracking.20issues.20for.20SIMD.3F.html#233117075">(Apr 04 2021 at 22:26)</a>:</h4>
<p>stdarch points to <a href="https://github.com/rust-lang/rust/issues/27731">https://github.com/rust-lang/rust/issues/27731</a>, libcore and libstd point to <a href="https://github.com/rust-lang/rust/issues/48556">https://github.com/rust-lang/rust/issues/48556</a>. They have almost exactly the same title, both opened by <span class="user-mention silent" data-user-id="116015">Alex Crichton</span>, and were opened 3 years apart.</p>



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<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/122651-general/topic/Why%20are%20there%20two%20tracking%20issues%20for%20SIMD%3F/near/233146632" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> bjorn3 <a href="https://rust-lang.github.io/zulip_archive/stream/122651-general/topic/Why.20are.20there.20two.20tracking.20issues.20for.20SIMD.3F.html#233146632">(Apr 05 2021 at 07:49)</a>:</h4>
<p><a href="https://github.com/rust-lang/rust/issues/27731">#27731</a> was the old plan for implementing SIMD (RFC 1199). This was introducing <code>extern "platform-intrinsic"</code> and then putting platform independent and platform dependent intrinsics there. <a href="https://github.com/rust-lang/rust/issues/48556">#48556</a> was for the new plan for implementing SIMD (RFC 2325). This was introducing a <code>std::arch</code> module with a one to one match between the C vendor intrinsics and the intrinisics in this module. These intrinsics have been implemented using <code>extern "platform-intrinsic"</code> when there were platform independent intrinsics or directly using LLVM intrinsics when there weren't.</p>



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<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/122651-general/topic/Why%20are%20there%20two%20tracking%20issues%20for%20SIMD%3F/near/233146812" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Mario Carneiro <a href="https://rust-lang.github.io/zulip_archive/stream/122651-general/topic/Why.20are.20there.20two.20tracking.20issues.20for.20SIMD.3F.html#233146812">(Apr 05 2021 at 07:52)</a>:</h4>
<p>Are both issues "open"? Or has one approach supplanted the other?</p>



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<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/122651-general/topic/Why%20are%20there%20two%20tracking%20issues%20for%20SIMD%3F/near/233146918" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> bjorn3 <a href="https://rust-lang.github.io/zulip_archive/stream/122651-general/topic/Why.20are.20there.20two.20tracking.20issues.20for.20SIMD.3F.html#233146918">(Apr 05 2021 at 07:54)</a>:</h4>
<p><a href="https://github.com/rust-lang/rust/issues/48556">#48556</a> has been stabilized for x86. The <code>extern "platform-intrinsic"</code> from <a href="https://github.com/rust-lang/rust/issues/27731">#27731</a> is used internally by <code>core::arch</code> and will be used by <a href="https://github.com/rust-lang/stdsimd">https://github.com/rust-lang/stdsimd</a>, which is the new plan for portable SIMD.</p>



<hr><p>Last updated: Aug 07 2021 at 22:04 UTC</p>
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